SIEMENS TYPE REHEATING FURNACES
placed near ports through which the waste gases were passing.
The same phenomenon occurs in the open-hearth melting furnace
when, by reason of the wear of the ports, the velocity of the air
and gas is reduced, and the jet of flame has a tendency to seek
the roof of the furnace, its thickness being normally that of the
gaseous stream, as computed according to Yesmann's formula.
At the corners of the hearth, close to the ports, a pocket of colder
gases is formed, and the bath freezes. In the Goujon works, at
Moscow, a case of this kind occurred with a furnace having a
hearth 14 m long. In order to correct this condition two burners
for naphtha were installed, one behind the other.
In the case under consideration a different procedure was
followed. The roof of the furnace was dropped close to the
heads, to the height required for the inverted weir, thus forcing the
flame of burning gases to lick the hearth, not only where it issued
from the ports, but also farther on. While estimating at its true
value this method of reconstruction for the type of heads fre-
quently used upon these furnaces, the author believes much better
results can be attained in another way.
Figs. 109 and 110 are two sketches of constructions which may
be employed in such a case. They are based upon the following
(a) The chilled gases are drawn off at the hearth level of the
reheating furnace; this method of removing the inactive gases
results in the uniform action of the hot gases upon the ingots and
favors their regular and uniform heating.
(6) The producer gas and the preheated air enter the heating
chamber of the furnace at a very low velocity, with the result that
combustion takes place throughout the entire chamber, and the
points of sharp combustion, close to the ports in the jet of flame,